1. Field of the Invention
The present invention relates to a steering wheel for a motor vehicle having a steering wheel module which supports electrical/electronic subassemblies and is attached to the steering wheel.
2. Background Art
Among other things, motor vehicle steering wheels include electrical/electronic subassemblies such as switches, display instruments, an airbag device, etc. In general, these subassemblies are assembled individually and independently of one another in or on the steering wheel or spokes of the steering wheel. To simplify assembly of these subassemblies, especially the control element, it has been suggested to arrange the subassemblies jointly on a base support so that they can be jointly attached to the steering wheel. Such a previously known steering wheel module will, as a rule, be attached to the pressure side of the steering wheel.
Electrical steering power-assist systems are being used in an increasing extent in motor vehicles. For these steering power-assist systems, the torque exerted on the steering wheel is necessary as a reference value so that using the detected torque the desired steering power-assist can take place. A torsion module is used to detect or measure the torque. A torsion module allows an angular offset between the steering wheel and the steering spindle when a torque is applied to the steering wheel in order to measure the torque.
Such teachings are, for example, known from DE 197 55 044 C1 and WO 99/40402 A1. In the case of the items disclosed in these documents, the torsion module is assembled between the steering wheel and the steering spindle separate from the steering wheel and also separate from the electrical/electronic subassemblies attached to the steering wheel. Accordingly, the torsion module including the mechanisms for detecting the rotational offset must be assembled separately and electrically connected. For this reason, a comprehensive functionality test of the steering wheel, including the torque detection device, cannot be performed until the necessary subassemblies have been assembled in the motor vehicle. In general, this is possible, but it means that the functionality test has to be performed by the vehicle manufacturer.